1. Technical Field
The invention relates to energy conversion devices, and particularly to a photovoltaic device.
2. Description of Related Art
Currently, solar energy is considered a renewable and clean energy source, and can also be used as an alternative source of energy other than fossil fuel. Solar energy is generally produced by photovoltaic cells, also known as solar cells. The photovoltaic cell or the solar cell is a device that converts light into electrical energy using the photoelectric effect.
Generally, the solar cell is usually made from silicon. Silicon employed in the solar cell can be single crystal silicon or polycrystalline silicon. Referring to FIG. 4, a conventional solar cell 30 according to the prior art, generally includes a silicon substrate 31, an intrinsic layer 32, a doped silicon layer 33, a front electrode 34, and a rear electrode 35. The silicon substrate 31 is made of polycrystalline silicon. In such case, the silicon substrate 31 is usually doped to form p-type silicon while the doped silicon layer 33 is usually doped to form n-type silicon. The intrinsic layer 32 is disposed between the silicon substrate 31 and the doped silicon layer 33 to create a p-i-n structure. The front electrode 34 is disposed on and electrically connected to the doped silicon layer 33. The rear electrode 35 is disposed on and electrically connected to, e.g. via ohmic contact, the silicon substrate 31. In addition, the solar cell 30 further includes a metal electrode 36 disposed on and electrically connected to the front electrode 34.
In use, if sunlight strikes the solar cell 30, the free electrons and holes are generated and separated to contribute a current. Particularly, the free electrons move toward the rear electrode 35 and the free holes move toward the front electrode 34. Current flow through the front electrode 34 can be collected via the metal electrode 36. Additionally, the electrodes 36 and 35 are connected to an external load. Trough the p-i-n structure, recombination speed of such mobile carriers is lowered by way of disposition of the intrinsic layer 32. Therefore, the photoelectric conversion efficiency on the solar cell 30 is increased.
Generally, the front electrode 34 is made of conductive metals, such as aluminum (Al), silver (Ag) or copper (Cu), which are usually not transparent to light. In order to increase the amount of incoming light, transparent conductive material, e.g. indium tin oxide (ITO), may instead be selected to form the front electrode 34. However, ITO material has drawbacks of, for example, being not chemically and mechanically durable, and having uneven distribution of resistance. As a result, the durability and the photoelectric conversion efficiency are relatively low.
What is needed, therefore, is a photovoltaic device that overcomes the above problems.
Corresponding reference characters indicate corresponding parts throughout the drawings. The exemplifications set out herein illustrate at least one embodiment of the present photovoltaic device, in one form, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner.